This invention relates to a patch applicator system for a transdermal patch which facilitates the application of transdermal patches, particularly transdermal patches having small dimensional characteristics.
A transdermal patch requires intimate contact with the site of application in order to effectively deliver a drug either locally or systemically. Such contact is usually achieved and maintained by means of an adhesive layer on the face of the patch. To protect the adhesive layer prior to application by the patch user, a releasable material is typically laminated to or applied over the adhesive which is then later removed and discarded before use. Removal of the release liner is often difficult without a mechanism to facilitate "peeling" it away from the adhesive.
A prior method used to accomplish this provides the release liner with a score or slit, such that upon bending of the release liner, a comer of the liner is exposed at the location of the slit to allow the liner to be peeled off.
Whether the release liner is scored or cut completely through, precision equipment is required. In addition to having to continually monitor and maintain such equipment, production problems including cracking of the release liner and imperfect or improper depth of the scores or cuts (for example, cutting into the adhesive or entirely through the patch) can occur. Further, even when the release liner is scored or cut as desired, separation from the adhesive layer can still prove to be cumbersome and difficult, particularly as the size of the patch is reduced.
Improvements in transdermal drug delivery technology such as those described in U.S. Pat. Nos. 5,474,783 and 5,656,286 both assigned to Noven Pharmaceuticals, Inc., Miami, Fla., have resulted in the ability to produce smaller and smaller patches without compromising the ability to deliver a therapeutically effective amount of the drug. Smaller patches, those less than 20 cm.sup.2 in surface area, and especially those less than 10 cm.sup.2, provide many advantages over larger patches.
The larger the patch, the greater the tendency of the patch to wrinkle, fold, become loose and/or dislodge from the application site, all of which reduces its ability to effectively deliver a therapeutic amount of drug or other material. Larger patches, due to their size, offer limited areas on a body for application and are often uncomfortable to wear as well as being unsightly. Since larger patches are more likely to be seen on an individual, the patch user can become more self-conscious or even embarrassed. Larger patches are also more costly to produce due to the need for greater amounts of drug, adhesives, excipients and additives. This in turn increases the risks of irritation and sensitization, especially since the possible application sites are reduced. Larger patches are more cumbersome to apply, adhering to itself or another inappropriate surface such as the fingers of the patch user, once the release liner is removed.
While smaller size patches offer numerous advantages over larger patches, the use of conventional scoring and cutting methods for the release liner creates greater disadvantages. As the size of the patch is reduced, the area that may be grasped when peeling the release liner away is also reduced. Smaller size patches also tend to increase the area of the patch which is touched before application, due to the need to manipulate the patch while the release liner is removed. This can result in loss of adherence before application of the patch. Touching the adhesive also increases risk of contamination to both the application site as well as the patch itself, which can negatively impact proper delivery of the drug or other agent. Further, contamination of the user's hands can result in contamination of sensitive areas of the user, such as the eyes or mouth, if touched by the user after application. Certain segments of the population, such as the elderly or those with arthritic conditions, may further find handling of smaller patches difficult. In view of the foregoing, it will be appreciated that providing a more effective and easily removable release liner would be desirable, particularly for smaller size patches.